MRI-Guided Intraluminal HDR Brachytherapy for Inoperable Malignant Biliary Tract Obstruction

Abstract

Aim: Malignant biliary tract obstruction (MBTO) leads to abdominal pain, jaundice, poor quality of life and portends a poor prognosis. Management of MBTO is a significant therapeutic challenge given that treatment with chemotherapy or radiotherapy has limited utility and percutaneous biliary drainage or stent insertion provides only transient symptomatic relief. Intraluminal HDR brachytherapy via catheters inserted percutaneously at the time of stent insertion can be effective in the management of inoperable MBTO. Here, we describe the workflow developed within our department for simulation and treatment using an intraluminal brachytherapy technique. Process: Delivery of bile duct brachytherapy requires the participation of multiple disciplines including interventional radiology (IR), medical physics, radiation oncology (RO) and radiation therapy with careful coordination of numerous tasks. A drain/stent and 1-2 treatment catheters are inserted into the patient's bile ducts by IR before the CT and MR simulation (sim). During the CT sim, multiple surview and low dose helical scans are acquired to verify the treatment catheter position and adjustments are made by the RO as needed. Once the position is finalized, a planning CT scan is done with IV contrast and the patient in voluntary breath hold. Then, the CT and MR sim images are fused. The CT is used to digitize the brachytherapy source path, while the MR is used for target and organs at risk delineation. Treatment is delivered 1-2 days after sim, with 15-25 Gy in 3-5 fractions using an Ir-192 HDR source. Radiographs are taken to confirm catheter position prior to each treatment. Benefits/Challenges: Brachytherapy can be used to treat the tumor at the same time as placement of a stent/drain, thus providing both symptom management and disease control. Although the patient is admitted for the IR procedure, the actual brachytherapy treatment is done on an outpatient basis with no anesthesia, thus treatment does not require significant time or resources in the brachytherapy suite. Patients often present with biliary obstruction emergently and stent/drain placement is booked urgently in IR with little notice to the radiotherapy department. The tight time line makes it difficult to facilitate communication between the multidisciplinary team, prepare staff, assemble supplies, and coordinate subsequent appointments. The CT sim process continues to evolve as new issues are identified with each patient. Variations in catheter/stent placement is a potential challenge and 2/8 patients have required reinsertion of angio-sheath by IR after problems were discovered during the CT sim. MR sim is not always possible depending on nature of inserted material (i.e. metallic stent or drainage sheath). Treatment catheters must be secured in place and covered with a dressing between appointments to prevent damage, change in position or obstruction. Patient education and cooperation is crucial to ensure proper care. Impact/Outcomes: In April 2021, our institution became the first in Canada to offer MRI-guided brachytherapy treatment for patients with inoperable MBTO. As of Jan 2022, 8 patients have been treated using this protocol. With each subsequent case, the time required for treatment delivery has decreased from 1 hour to 30 minutes per fraction and sim processes optimized. This treatment option has potential to improve the quality of life in patients with minimal therapeutic options.